biology genetics

Question 1

What is DNA and where is it found

Answer 1

DNA is the molecule that carries genetic information. It is found in chromosomes within the nucleus of cells.

Question 2

Describe the structure of DNA

Answer 2

DNA is a double helix made of nucleotides (phosphate, sugar, base). Bases pair A-T and C-G, held by hydrogen bonds.

Question 3

What is a gene?

Answer 3

gene is a length of DNA that codes for a specific protein.

Question 4

What is an allele?

Answer 4

An allele is a different version of a gene.

Question 5

What is the difference between haploid and diploid cells?

Answer 5

Haploid - n
One copy of genetic material subdivided into chromosomes
eg gametes

Diploid - 2n
Two copies of genetic material subdivided into chromosomes
eg zygote

Question 6

What is a karyotype and what is it used for?

Answer 6

A karyotype is a picture of chromosomes used to determine sex and detect chromosomal abnormalities.

Question 7

How does DNA control cell function?

Answer 7

DNA controls cell function by:
* directing the production of proteins,
* like enzymes,
* which regulate cellular processes.

Question 8

What is a gene mutation and what can cause it?

Answer 8

A gene mutation is a change in the DNA base sequence. Causes include ionising radiation and some chemicals.

Question 9

What is mitosis?

Answer 9

Mitosis
When a cell divided the chromosomes double by replacing itself. The cell then splits once to make 2 indentical cells. This is used for growth and repair

• Has two cells that are indentical
• Growth, repair, replace
• Creates diploid cells

Question 10

What happens to chromosomes before mitosis?

Answer 10

Before mitosis, chromosomes are exactly duplicated to ensure each daughter cell gets a complete set.

Question 11

What are the stages of mitosis (PMAT)?

Answer 11

Prophase, Metaphase, Anaphase, Telophase.

Question 12

What are the roles of mitosis?

Answer 12

Growth, repair, replacement of cells, and asexual reproduction.

Question 13

What is meiosis?

Answer 13

Meiosis
- Has 4 cells, all unique
- Reproduction
- Creates haploid cells - sperm and egg

Many different stages which creates variation between all the cells produced. This ensures all babies are unique. The function of meiosis is used for reproduction is why it produces haploid cells

Question 14

How does meiosis lead to variation?

Answer 14

By forming new combinations of maternal and paternal chromosomes in gametes.

Question 15

What is sexual reproduction?

Answer 15

The fusion of two haploid gametes to form a diploid zygote, producing genetically different offspring.

Question 16

What are the advantages and disadvantages of asexual and sexual reproduction?

Answer 16

Asexual: fast, no mate, identical;
Sexual: slower, needs two parents, but creates variation.

Question 17

What is a genotype?

Answer 17

The genetic makeup of an organism (alleles present).

The genes responsible for the characteristics eg eye colour

Question 18

What is a phenotype?

Answer 18

The observable traits of an organism.
The physical characteristics of an individual eg blue eyes

Question 19

What is the difference between dominant and recessive alleles?

Answer 19

Dominant alleles are always expressed; recessive alleles only when no dominant allele is present.

Question 20

What is codominance? Give examples.

Answer 20

Both alleles are expressed. E.g., striped flowers (RW) or blood type AB (IAIB).

Question 21

What is the difference between homozygous and heterozygous?

Answer 21

Homozygous = two same alleles; Heterozygous = two different alleles.

Question 22

What is a monohybrid cross and what ratios can it produce?

Answer 22

a phenotypic ratio of 3:1 (dominant to recessive), and a genotypic ratio of 1:2:1 (homozygous dominant to heterozygous to homozygous recessive).

genetic diagram for one trait; produces 3:1 or 1:1 phenotypic ratios.

Question 23

What is a test cross used for?

Answer 23

To determine the genotype of an individual by crossing it with a homozygous recessive.

Question 24

How is sex-gender inherited in humans?

Answer 24

Females are XX, males are XY. The sperm determines the sex of the offspring

Question 25

What is a sex-linked characteristic? Give an example.

Answer 25

A trait from a gene on a sex chromosome, often affecting one sex more. Example: haemophilia.

Question 26

What are pedigree charts used for?

Answer 26

To trace inheritance and determine probable genotypes and phenotypes in families.

Question 27

What is variation and what types are there?

Answer 27

Differences between individuals. Phenotypic (physical traits) and genotypic (genes).

Question 28

What is the difference between discontinuous and continuous variation?

Answer 28

Discontinuous: distinct traits (e.g., blood type); Continuous: range (e.g., height).

Question 29

How do you investigate variation?

Answer 29

By collecting data and presenting it in bar charts (discontinuous) or histograms (continuous).

Question 30

What is natural selection?

Answer 30

Process where better-adapted individuals survive, reproduce, and pass on favorable alleles. Species ability to adapt to a changing environment

Question 31

What are adaptive features?

Answer 31

Inherited traits that increase an organism’s fitness specific traits that have evolved in organisms to help them survive and reproduce in their specific environment.

Question 32

How can you identify adaptive features from a species?

Answer 32

By interpreting characteristics that help it survive, like camels storing fat in their humps.

Question 33

What is evolution?

Answer 33

The change in adaptive features of a population over time due to natural selection.

Question 34

What is the difference between natural and artificial selection?

Answer 34

Natural: environment selects traits. Artificial: humans select traits (e.g., breeding).

Question 35

What is selective breeding and how is it done?

Answer 35

Choosing parents with desired traits, breeding them, and selecting offspring with those traits to improve crops or animals.